Concentration apparatus and method

ABSTRACT

975,655. Froth flotation. DENVER EQUIP MENT CO. Dec. 11, 1961 [April 5, 1961], No. 44318/61. Heading B2H. A process for the concentration of minerals, e.g. of copper, in an ore by froth flotation in a cell, in which one constituent of the ore rises and is separated from the upper part of an ore pulp formed of a mixture of ore particles and a liquid, e.g. water, and at least one other constituent settles in the ore pulp to form tailings, is characterized in that at least a fraction of the settled particles are moved into a vortex beneath the flotation cell to separate the lighter from the heavier of said particles, the heavier particles being discharged continuously from the lower end of the vortex. In the flotation cell 60, Fig. 4, the ore pulp, which enters through a conduit 74, is agitated by an impeller 61 driven by a rotary shaft 62. The shaft 62 is enclosed in a casing 64 closed at its upper end by a bonnet 65 to which air is supplied at 66. Air passes down the casing and a froth is formed by the impeller 61, which froth rises to the top of the cell and is removed by a rotating horizontal paddle 71. The tailings and middlings settle in the cell and enter a conical separator 78 fitted directly beneath the impeller 61. As the impeller rotates a vortex of pulp is created in the separator 78 and the heavier middlings leave through an outlet 80 to be reprocessed whilst the tailings and fine middlings leave eventually over a weir 75, adjustable by means of a hand wheel 76. The speed of the vortex may be controlled by vertical adjustment of the impeller 61 using slotted support plates 69, 70 and the impeller may be fitted with adjustable blades on its underside, Fig. 5 (not shown), to increase the speed of the vortex. The separator 78 has a rubber lining 81 to prevent damage, and air may be supplied tangentially to the outlet 80 to prevent a blockage of the heavier particles therein. The invention may be applied to a multi-cell flotation machine 10, as in Fig. 1, which machine has a feed inlet 11, a tailings outlet 12 and the froth concentrate is removed in a launder 13 with an outlet 14. Conical separators 15a, b, c, d and e are fitted to the last five cells of the machine 10. The heavier middlings particles from the separators 15a to e are fed to a classifier 17, where slimes are removed through a line 18, the raked solid product being fed to a ball or rod mill 21 to which fresh feed is also led by a line 20. The discharge from the mill 21 is fed to a screen 22 to remove outsize particles through a line 23, and the feed from the screen 22 is led to a conditioner tank 25 and through a pump 26 to the feed inlet 11 of the machine 10. Thus the heavier middlings particles are reprocessed to recover a proportion of the ore values they contain. The arrangement shown in Fig. 1 is suitable for use with an ore which settles slowly. In the case of an ore in which the heavier particles settle rapidly, the conical separators are fitted below the first few cells of the machine series, with one other separator fitted to a cell towards the tailings discharge end of the machine, Fig. 2 (not shown). The separators may have outlets of decreasing diameters, and thus discharge capacities, and the combined outlet discharge may be fed to a cyclone separator to remove fine particles to waste before feeding the heavier particles back to the ball mill. As a further alternative, the combined outlet discharge from the conical separators may be fed to a concentrating table or jig to remove fines and slimes, the concentrate of this step being removed as a final product whilst the middlings are returned to a classifier as in Fig. 1. In another alternative, where the ores to be concentrated settle very rapidly, the outlets from the first conical separators may be led to waste and only the output from the last separator is reprocessed. Alternative arrangements of impellers and conical separators are shown in Figs. 6, 7 and 9. In Fig. 6, the conical separator has an annular portion 88 with a separate agitator 90 driven from the impeller, and a tangential liquid inlet 91 is provided to increase the speed of the vortex. In Fig. 7, the outlet from the conical separator is fed tangentially to a cyclone separator 95, slimes being removed through an outlet 96, whilst a cleaned and graded concentrate is removed through an outlet 97. The conical separator of the invention may also be employed with the impeller shown in Fig. 9, which has depending fingers 102, or with a squirrelcage rotor, Fig. 10 (not shown), disposed for rotation inside a fixed squirrel-cage enclosure. Specification 456,249 and U.S.A. Specification 2,107,289 are referred to.

July 23, 1963 A. c. DAMAN ETAL 3,093,818

' CONCENTRATION APPARATUS AND METHOD Filed April 5, 1961 4 Sheets-Sheet 1 FEED/N ffiQEEFEHHFiHFREHHEP-IHHH g; 30 [1 35d 38 35a 34 32 INVENTORS. A C. Daman Thomas S. Bailey, Jr.

ATTORNEYS July 23, 1963 A. c. DAMAN ETAL CONCENTRATION APPARATUS AND METHOD 4 Sheets-Sheet 2 Filed April 5, 1961 HEP-15335355533331 IIEED IN 3/ L l/ IE INVENTORS. Arthur C. Damon Thomas S. Bailey, Jr

78 82 BY 79 a g t A ORNEYS July 23, 1963 A. c. DAMAN ETAL CONCENTRATION APPARATUS AND METHOD 4 Sheets-Sheet 3 Filed April 5, 1961 INVENTORS 8 Arthur C. Daman Thomas S. Bailey, Jr?

NE YS July 23, 1963 Filed April 5, 1961 A. c. DAMAN ETAL 3,098,818

CONCENTRATION APPARATUS AND METHQD 4 Sheets-Sheet 4 FEED IN maaaaaaaaaaaaaaai INVENTORS. Arfhur C. Daman Thomas S. Bailey, Jr

ATTORNEYS United States Patent 3,698,818 CONCENTRATION APPARATUS NETHQD Arthur C. Daman, Denver, Colo., and Thomas S. Bailey, Jr., Johannesburg, Transvaal, Republic of South Africa, assignors to Denver Equipment Company, Denver, Colo., a corporation of Colorado Filed Apr. 5, 1961, Ser. No. 100,879 9 Claims. ((11. 209-169) Our invention relates to methods and apparatus for concentrating the valuable constituents of a mixture of solids in liquids, such as an ore pulp, and has particular application but is not limited to improvements in froth flotation treatments.

Flotation concentration is widely used in ore milling and similar treatments requiring a metal or other valuable constituent to be separated from other mineral or gangue with which it is associated. Such a treatment requires separation of such constituents as by crushing and grinding, in which action the separated particles are reduced to a flotation size. In the process a pulp is formed, the liquid component of which acts as a carrier vehicle. Prior to flotation, the ore is conditioned by mixing with one or more reagents as collectors and the conditioning may include frothers and modifiers as well.

Various supplemental concentrating procedures have been proposed or used in the past as an adjunct to the flotation concentration. Denny et a1. Patent No. 2,107,289 illustrates one arrangement of this type which has provided an adjunct concentration applied to a unit cell flotation machine. Daman Patent No. 2,122,028 illustrates another arrangement in which a jig is located underneath a unit cell machine as a mineral trap to collect some of the heavier mineral concentrate which does not collect in the froth concentrate. According to the teachings of each of said patents, the underflow material passing into the adjunct concentrator is held therein and only occasionally discharged from the trap. While the flotation cell operation is continuous, these machines provide only intermittent discharge of the adjunct concentrate, rather than a continuous discharge as performed by our process.

In the usual flotation operation, ground ore in a pulp is conditioned and then subjected to agitation and aeration influences in a series of cells in which the mineral or other valuable constituent, responding to the influence of the collector reagent, is elevated in each cell by the buoyant effect of the air introduction and collects on the surface in a froth, where it is removed by overflow or the action of mechanical Skimmers. While flotation machines and reagents have been improved to such an extent that the flotation separation per se produces a relatively high recovery, there is always a substantial tailings loss in such separation, i.e., concentrate mineral passing from the treatment with the tailings, and a substantial recovery improvement can be attained it the adjunct concentration can be performed efficiently at low cost. 7

Many operations utilize a hog-trough flotation machine in which the cell divisions of the unit permit a direct or substantially direct flow of pulp along the bottom of the machine between its feed inlet and tailings discharge outlet. Solids settling on the bottom are swept along by the action of the impellers and finally discharge through the tailings outlet. As such solids accumulate, concentrate material which otherwise might float will be entrained in the bed of solids and carried from the treatment as tailings. Coarse middlings comprise a substantial portion of the settled solids and likewise represent a tailings loss.

Operating experience has demonstrated that if the ore is ground too fine, a large amount of the concentrate ma Patented July 23, 1963 terial will be reduced to extremely fine sizes; and best recovery is obtained where a minimum amount of the concentrate material is in extremely coarse or extremely fine sizes. As the grinding cost is a substantial part of the entire milling expense, it is good economy, as well as beneficial to the recovery, to avoid excessive size reduction in the grinding stage for the entire ore charge and the present trend is toward coarser grinds. This practice produces substantial amounts of coarse concentrate material and coarse middlings, which collectively represent only a small fraction of the ore, but are valuable enough to warrant additional size reduction so as to obtain improved recovery.

The present invention involves a distinct departure from prior practices in having an adjunct concentration unit or stage which collects settled solids from an associated cell and subjects said solids to a sorting action for separation of valuable constituents from gangue in a simple, efiicient and economical manner. One of the innovations of the present invention is that the adjunct concentrator operates continuously and discharges continuously in contradistinction to the intermittent batch type discharge of the prior art.

Accordingly, it is an object of our invention to provide a dual concentration in a single flotation action which is simple, eificient and economical and substantially reduces tailings losses at the flotation stage.

Another object of this invention is to provide a simple, durable and efficient flotation apparatus providing a dual concentration in a single flotation stage.

A further object of our invention is to provide series arrangement of secondary concentration apparatus which provides a selective concentration of graded concentrates.

Yet another object of our invention is to provide a dual concentration in which mineral concentrate and a middlings product are separately recovered and removed from a flotation treatment without increasing the power input over that required for the primary concentration of said treatment.

A still further object of this invention is to provide a combined classification and flotation concentration in which the concentrate material reduced to a flotation size is recovered as a froth concentrate while coarse sizes of middlings and gangue are subjected to a separate concentration with oversize middlings and concentrate being returned to the grinding stage for additional reduction and further concentration.

Further objects and advantages of our novel method and apparatus, including novel arrangements and combination of parts, according to the invention will be apparent to persons skilled in the art through study of the following description. The practice of the invention will be readily understood by reference to the accompanying drawings. In the drawings, in the several views of which like parts bear similar reference numerals:

FIG. 1 is a flow sheet representation of a typical circuit using one form of our multi-cell concentrating apparatus adapted to perform the novel methods of our invention;

FIG. 2 is a second typical circuit having another form of multi-oell concentrating apparatus of our invention used in performing the novel methods of our invention;

FIG. 3 is still another typical circuit using our concentrating apparatus in the practice of the novel methods of our invention, and utilizing a secondary concentration separate from the flotation circuit;

FIG. 4 is a front elevation of a typical Denver Sub- A flotation cell incorporating our novel concentrating means as an adjunct to the flotation apparatus or cell and which is partially broken away to show arrangement of interior parts;

FIG. 4A is a top plan view of the concentrating apparatus of FIG. 4 shown as detached from the cell of FIG. 4 and drawn to an enlarged scale;

FIG. 5 is a fragmentary front elevation of another type of flotation cell, broken away to show the arrange- 'rnent of interior parts and illustrating another form of apparatus for cooperation with a flotation cell for Ohtaining another concentrate from material not collecting in the froth concentrate of such cell;

FIG. 6 is a fragmentary front elevation of another flotation cell, partially broken away to show arrangements of interior parts with which the supplemental concentrator of our invention has been incorporated in a different structural form;

FIG. 7 is another fragmentary front elevation of still another typical flotation cell, partially broken away to show the interior arrangement of parts and which utilizes a supplemental or adjunct concentrator according to our invention and a secondary treatment of said supplemental concentrate;

FIG. 8 is a flow sheet representation of another multiple cell flotation machine utilizing a different circuiting arrangement employing supplemental concentrating apparatus according to our invention;

FIG. 9 is a vertical section of yet another type of commercial flotation cell with which the concentrating apparatus of our invention is combined; and

FIG. 10 is a fragmentary vertical section of still another type of commercial flotation cell with which the concentrating apparatus according to our invention has been combined.

Before describing the arrangements shown in the drawings in detail, we wish it understood that said drawings are but exemplary of novel apparatus arrangements which may be used in the practice of our invention and are not intended as a limitation of the invention, the scope of which is defined in the appended claims.

As it is quite common in flotation circuiting to have a substantial amount of coarser sizes in the feed to the flotation circuit, because the grinding circuit is regulated to produce a minimum of fines and the larger sizes of the pulp often settle in substantial quantity on the bottom of the cell where they tend to spread beneath and around the impeller, this results in a progressive buildup of settled solids on the bottom of the cell which contain a substantial amount of concentrate. Concentrator apparatus according to our invention is usable with various mechanicaltype flotation cells, particularly hog-trough machines, to overcome the problems of concentrate loss through such settling. In addition, the various arrangements shown and described herein, provide cooperation between the blades on the bottom of the impeller, and the upwardly opening, conical separator beneath the impeller that establishes a continuous vortex in the separator which has characteristics of a centrifugal separator, with continuous segregation of a downwardly discharging, heavier or coarser fraction from said separator.

A typical multi-cell apparatus according to our invention will be effective in a separation of a coarse from fine, heavy from light, and in special sand removal operations. One or a plurality of our separators are selectively spaced at intervals along the bottom of cells in a multi-cell machine, such as the multi-stage flotation machine 10 shown in FIG. 1 having a feed inlet 11 at one end, a tailings discharge 12 at its opposite end, and a froth overflow launder 13 extending along a side of the series of cells and which has a single outlet 14. Concentrators 15a, 15b, 15c, 15d and 15e are disposed beneath the impellers of the last five stages or cells.

In such an arrangement, the settled solids which are not elevated or floated by the aeration or agitation are swept or drawn along the bottom beneath the impeller until they are drawn into and reach the vortex influence of separator 15a, wherein the coarser or heavier settled particles are separated in the centrifugal action therein and are continuously removed through the outlet at the bottom of the separator into a discharge line or conduit 16.

The vortex action in separator 15a causes the lighter fraction of the settled solids to be crowded upwardly into the bottom portion of the cell in a displacement action While the larger or heavier particles travel through the pulp to the bottom of the separator. So much of the elevated material as returns to the flotation machine without suspending in the pulp therein flows toward the final outlet 12 until it is drawn into and subjected to the action of separator 15b.

The treatment in separator 15b is essentially the same as in separator 15a with more of the concentrate or middlings material removed as an underflow product. Each of the separators 15c, 15d, 15e progressively subjects the entering matter to a separation according to size or specific gravity for discharge of the separated underflow through a common discharge line or conduit 16. The residual solids in the last cell, which are not removed by separator 15e, are removed as waste through the tailings outlet 12 of the machine. The combined separated heavier or coarser fractions from the five separators 15a through 15c, are conducted by iine 16 to a classifier 17 wherein a slimes fraction is removed through a waste overflow line 18 and a raked product is delivered into another line 19 discharging into the feed inlet 20 of a ball mill 21. Mill 21 may have other feed introduced through a supply line 20 if desired.

A screening unit 22 is mounted at the discharge end of mill 21 for removal of tramp oversize material which is discharged from the treatment through line 23, while the reground middlings material passing through the screen 22 is delivered by line 24- into a conditioner or surge tank 25, where additional reagent may be supplied. Pump 26 circulates the reground middlings product from tank 25 through a line 27 for return through the feed inlet 11 into the multi-stage flotation apparatus 10. In some multistage flotation circuits there is not a suflicient time interval for middlings and mineral constituents too large to float to settle on the bottom of the forward cells of the operation. The circuit of FIG. 1 is particularly effective under such conditions and provides an efiicient collection and separation of middlings for regn'nding and return to flotation. In such a treatment, the circulating load is held to a minimum by elimination of slimes, and the quantity of coarse concentrate and middlings subjected to additional grinding is only a fraction of the total feed and as taiiings losses are substantially reduced by the regrinding, the additional recovery is obtained at relatively low cost.

Another circuiting arrangement has been illustrated in FIG. 2 which is particularly suited for treatment of quick settling constituents of the pulp. The circuit of FIG. 2 includes a multicell flotation apparatus 30 of the hogtrough type having a feed inlet 31, a tailings discharge 32, and a common froth concentrate overflow launder 33 for the series of cells discharging through a nipple 34. Four separator cones 35a, 35b, 35c and 35d are mounted beneath the impellers of the first four cells; and a fifth separator 35e is mounted beneath a subsequent cell toward the tailings discharge end of the apparatus.

These separators may have underflow outlets of varying size. In a preferred arrangement, cones 35a and 35b may have outlets on the order of 1%" or 1%" diameter while 35c and 35d will have 1'' outlets. The greater discharge capacity of the first two separators serves to remove most of the settled mineral from flotation, together with coarser middlings. The next two separators are of lesser discharge capacity, as the major portion of the solids entering such separators comprises tailings which are returned to the flotation cells for final removal with the tailings discharge through outlet 32. As shown in FIG. 2, the under-flows of these separators are delivered into a line 36. The cone 35c underflow. while cont-aim ing a substantial amount of tailings, is a product too valuable to waste which is primarily middlings and is conducted through a line 38 to combine with the discharge of line 36 as feed to a pump 37.

The combined discharge of the separators 35a, 35b, 35c, 35d and 35e is pumped through a tangential inlet 39 of a cycloneatype separator 40. A finer or lighter fraction of the separation therein is removed as waste through a conduit 41 and the thickened middlings underflow is conducted by a line 42 to the feed inlet 43 of a ball or rod mill 44. The remaining portion of this circuit is substantially identical with that described in reference to the circuit of FIG. 1. Tramp oversize is discharged through a line 46 after rejection on a screen 45 treating the discharge of the mill 44 and a reground middlings fraction is discharged into a conditioner or surge tank 4-8 through a line 47. A pump 49 recirculates the conditioned pulp through feed inlet 31 of flotation machine 30.

FIG. 3 illustrates still another circuiting arrangement providing additional treatment of the recirculated middlings and is similar to the circuit of FIG. 2, except that the discharges of the respective separators 35a through 3512 are treated for removal of constitutent solids before the remaining portion is subjected to regrinding. The combined discharge of cells 35a through 352, comprising middlings and coarser sizes of the valuable constituent is subjected to further treatment. The treatment circuit as shown in FIG. 3 includes a concentrator, such as a concentrating table 51 or a mineral jig (not shown) to which said combined discharge is fed by a line 52. The slimes and other tailings in fine sizes are discharged from the table as waste and are removed by a line 53. The concentrate of the ta-bling separation is removed through a line 54 as a final product, while the middlings are removed at 55 and delivered as feed to a classifier 56. Any remaining slimes and other fine waste constituents are removed in the classifier overflow 57, while the classifier raked product containing most of the collected concentrate material is conducted through a line 58 and discharged as feed into the inlet 43 of a ball mill 44, for regrinding and further treatment in the same way as described with reference to the circuits of FIGS. 1 and 2.

FIG. 4 represents a typical Denver Sub-A flotation cell to which a conical separator according to our invention has been connected. As illustrated, this cell is an intermediate cell of a multicell machine and comprises a cell or tank 60 having a centrally disposed impeller 61 mounted on a rotary shaft 62 driven by a sheave 63 of a power transmission system (not shown). The impeller shaft 62 is disposed within a 'hollow column 64, closed at its upper end by a bonnet 65, which has an air inlet nipple 66. Interconnected bearing assemblies 67 and 68 are supported on slotted adjustment plates 69 and 70 for vertical adjustment of the entire assembly supporting the impeller. A froth skimmer or rotary paddle 71, driven by a suitable transmission system 73 at a rate determined by a motor and speed reducer assembly '72 is provided for removal of froth from the surface of the liquid in the cell. Feed enters the cell through a feed conduit 74 and is delivered onto the hooded impelle-r 61. The tailings discharge from the cell passes over a weir 75 positioned by a hand wheel 76 on a rod 77 and comprises the feed to the next cell in the series.

A bottom opening in the cell is enclosed by a generally conical separator 78 attached directly below and in proximity to the impeller 61 which has its. bottom blades in position to produce a vortex condition within the separator. By having the bottom of the impeller in close proximity to the open top of the separator, we have found that substantially no power loss is encountered. As some materials tend to pack too tightly in the centrifugal action of the vortex to the detriment of the sorting action, we provide an inlet nipple 7? adjacent the bottom of separator 78 for delivery of a tangential flow of a lubricating fluid, such as water, so as to maintain a desired fluidity to suit the sorting requirement of the separation. The underflow outlet 80, preferably having an internal thread as shown, may be of any suitable diameter to accommodate the discharge of said separator.

Settled solids in cell 60 accumulate on the bottom and entrain some solids which otherwise would float or suspend in the pulp and said settled solids are drawn into separator 78 by the vortex influence and subjected to the sorting action therein. As the separator 78 is subjected to a considerable abrasive action in such sorting operation, we preferably provide a rubber liner 81 which extends from the outlet nipple to the top peripheral surface adjacent the flange 82, so as to reduce wear and said liner may be replaced when it deteriorates to preserve the separator structure.

For some treatments, at high intensity vortex formation may be required, and the arrangement shown in FIG. 5 is well suited for this purpose. As shown, the impeller has blades or vanes 84 on its undersurface positioned in close proximity to the top of the separator and of such size and disposed at an angle which will impart a high intensity centrifugal movement to the material in separator 78. Again in this arrangement, an inlet 79' is included to provide fluidity control and as the flotation machine has provision for adjusting the elevation \of the impeller and the elevation of blades 84 relative to the top of separator 78, the intensity of the vortex action may be closely controlled.

In FIG. 6 a slightly different type of separator cone 85 is shown having a discharge nipple "86 at its bottom, an upwardly opening conical portion 87, and an annular extension portion 88 above the conical portion 87. An inlet 91 in annular portion 88 supplies lubricating fluid to the top portion of the separation zone. A shaft 89 is secured on and depends from the bottom of the impeller and a bladed agitator 90 is mounted at the lower end of said shaft in approximately the same elevation as the .inlet .91 so as to supplement the action of the impeller in producing an intense vortex effect. This arrangement is particularly effective when substantial dilution is required in the separation. The agitator mixes the liquid input .through'liquid inlet 91 with the pulp from the cell and provides thorough washing of the solids moving under the centrifugal influence in the separator. Such washing removes entrained slimes and fines from the coarser sizes and provides an essentially clean underflow discharge.

FIG. 7 shows Ia different form of conical separator 78a having its upper opening beneath the impeller '61 and this separator has no water inlet for dilution of the pulp under treatment. The underflow discharge through the cone outlet 80a passes through a conduit 8017. at a substantially lower elevation to establish a hydraulic head directinga tangential flow into another cyclone-type separator 95, the roverflow discharge of which passes through an outlet 96 and its underflow discharge passes through an outlet 97. The additional treatment of the underflow discharge from separator 78a in the hydro-cyclone 95 removes slimes and finer particles through the upper outlet 96 while a cleaned and graded concentrate is directed through the bottom discharge outlet 97.

Still another circuiting arrangement is shown in FIG. 8 utilizing a multi-cell flotation machine 30, similar to the apparatus arrangement of FIG. 3, including plural conical separators 35a through 35e. The circuit of FIG. 8 differs from the FIG. 3 circuit in the distribution of the underflow products of the separators. When the ore under treatment has a substantial quantity of fast settling sands or other tailings constituents, some or all of the separators 35a through 35d may be used for tailings elimination, and the underflow of said separators may-be passed directly to waste. Middlings are collected and'segregated in separator 35a and the concentrate material is removed as underflow while sands separated therein are returned to the machine 30 and are finally discharged at 12. The middlings preferably are returned to a ball or rod mill in the initial lore preparation stage of the plant circuit as separator 35e does not produce enough underfiow material to require a separate grinding mill installation.

FIGS. 9 and 10 are examples of other types of flotation cells which are adapted for modification to utilize the novel separator apparatus of our invention. In FIG. 9, the cell 100, has a centrally-disposed shaft 101 mounted for rotation and carrying an impeller 102 at its lower end, the periphery of which comprises a series of downwardly extending fingers in closely spaced arrangement. The impeller 102 is mounted in close adjacency to and spaced from the cell bottom and being of greater diameter than the top of conical separator '7 8 encloses the opening to the separator and the impeller fingers assist the vortex formation therein.

FIG. 10 illustrates another type of flotation cell 104 having a rotary shaft 105 carrying a squirrel-cage rotor 106 disposed in a squirrel-cage enclosure 107. Pulp is drawn into the enclosure through bottom openings in the impeller 106 and is subjected to beating influence in its passage between the bars or rods of the squirrel-cage of the impeller and again in the passage through the rods or bars of the squirrel-cage enclosure. Mineral too coarse to float and oversize gangue settling in the cell pass into the separator where the vortex action provides the sorting action necessary to return gangue to the cell, While collected middlings mineral is discharged through the underfiow outlet 80.

In actual tests, a separator according to our invention was fitted to one cell of a multi-cell machine, in order to determine whether a middling product could be produced containing a considerable proportion of the copper values that did not =float readily in the cell. Preliminary tests were run to determine the value of the product:

TEST 1 In this test, a separator was mounted beneath the impeller, water was introduced through the cone, and operated continuously for several hours.

The product discharge from the separator was assayed and gave the following value:

Total copper 3.21%

TEST 2 In this test a 1" hose was fitted to the cone and discharged continuously without addition of water.

This was sampled continuously for 6 hours with the following result:

Total copper 1.30%

During this period the tailing from the last cell was sampled, giving the following result:

Total copper 0.63%

Comparative tests of a similar nature on similar units without separators, were conducted with the following results:

Tailing for the day Total copper 0.80%

These results indicated that a considerable proportion of the content of the tailings copper was being recovered with our separator and No. 3 test was then instituted, the samples being screened and assayed.

TESTS In this test, the separator product and tailing from the last of a bank of cells were screened and assayed with the following result:

Cone product: Total copper 1.20 Last cell tailing: Total copper 0.72

Comparative cell, no separator Tailing: Total copper 0.93%

Separator Screen Analysis Cumula- Assay, Distribu- Mesh Size of Screened Percent tive, Percent tion,

Fraction percent Total Cu Percent Total Cu Comparative Cell Tailing for Same Period Onmula- Assay, Distribu- Mesh Size of Screened Percent tive, Percent tion,

Fraction percent Total Cu Percent Total Cu During this period the flow was measured and also specific gravity determined:

The average flow was 7.5 seconds per gallon of pulp with an average pulp density of 1.45; assuming the specific gravity of solids at 2.9, this equals 30.8 dry tons of prodnot per 24 hours.

30.0 tons of dry solids per 24 hours discharged by a separator and assaying 1.2% total copper equals 739.2 pounds per day of additional copper recovered from the separator in this circuit.

From the above, it will be seen that our separator is capable of recovering a substantial proportion of the copper normally discharging with the tailings otherwise representing a recovery loss.

In another plant test processing copper ore, an installed bank of flotation machines was modified to include separators according to our invention, and the following tabulated results indicate the reduction in copper ore lost to tailings when the separators were included:

Percent First shift: Copper Plant tailing 0.93

Tailing from bank using separator 0.62

Second shift:

Plant tailing 0.80

Tailing from bank using separator 0.62

In all the arrangements of flotation cell and conical separator shown in the drawings, the top of the separator is located beneath and in close adjacency to the impeller so that the sweep of its rotation is utilized as the power source for the centrifugal movement of material within the separator.. The centrifugal action therein causes heavier or coarser solids to segregate and pass through the underflow outlet in a substantially packed condition due to the diminishing space of the separator as said constituents approach said outlet.

In the same action, liquid and lighter or smaller sizes are displaced by or are unable to penetrate the higher density underflow material adjacent the outlet, and this sorting action is maintained throughout the period of continuous operation. If the solids in the cone tend to pack so tightly that excessive wear on the cone surfaces results or discharge is delayed, water or other lubricating fluid may be introduced through the inlet 79 or equivalent.

This lubricant introduction is effective in loosening and elevating finer or lighter sizes which may have been entrained in the material descending to the underflow outlet so that the material passing through said outlet is essentially clean and in suitable condition for the subsequent treatment, such as shown in FIGS. 1, 2 and 3.

In the various circuiting arrangements illustrated in FIGS. 1, 2, 3 and 8, settled solids containing an appreciable quantity of mineral or the valuable constituent of the treatment which otherwise would pass from the treatment and represent a metallurgical loss to the operation is collected, segregated and separated as product with resulting reduction in tailings losses. in addition, middlings which otherwise would be lost or lessen the grade of the concentrate product, if combined therewith, are treated in closed circuit with a size reduction stage to return to the flotation stage in suitable size and condition for final recovery of substantially all the concentrate content of said middlings.

By this arrangement, excessive grinding of the entire ore charge is avoided and the quantity of material subjected to regrinding in the middlings treatment is only a small fraction of the entire charge but contains enough concentrate material which is eventually removed as product to substantially improve recovery. The supplemental separation of the conical separator provides additional recovery of the collected concentrate material and segregates middlings material therewith which may be reground and refloated or otherwise treated to attain such improved recovery, and said separator rejects waste material which is returned into the flotation machine where it finally discharges as tailings.

With reference to the various structural modifications previously described, it should .be understood that the shaping, size and arrangement of the separators may be varied according to the requirements of a :given treatment and the same is true of the arrangement of blades or suspended agitators on the underside of the impellers. Features described with reference to one drawing disclosure may be incorporated in any of the others and similarly with respect to the circuiting following the segregation treatment, any of the circuiting practices shown in relation to one term of separator may be applied to all.

The various circuits illustrated disclose the collection of settled solids, their treatment in a vortex zone to obtain a segregated coarser or heavier fraction, usually middlings, which fraction is subjected to a size reduction and the fraction after size reduction is introduced as feed to a flotation stage. The drawings illustrate the return of such fraction for introduction with the original feed to the machine, but obviously such fraction may be returned to any flotation stage where it can be eifectively handled.

Also in preferred practice, we provide a plurality or succession of separators operating in conjunction with a plurality of the flotation cells. With certain pulps, only a single stage may be required and it will be understood that the use of a single stage separator is within the contemplation of our invention.

In treatments where a substantial amount of concentrate material other than middlings settles in the cells, it will be advantageous to have a concentrating stage incorporated in the recirculating treatment. We have shown the use of concentrating tables and cone separators and described the use of mineral jigs as an alternative concentrating apparatus. It is within the contemplation of our invention that any suitable concentrating treatment may be provided and the arrangement of equipment for this purpose shown in the drawings is merely exemplary of the treatment to be performed.

While the examples of the practice of our invention have involved a flotation concentration of metallic ores, the use of the invention may be applied to flotation of non-metallics, such as potash ores, for example, or in any other treatments where a middlings material tends to settle in the cells and represents a tailings loss.

As the novel methods and practices of our invention may be performed in a variety of apparatus as exemplified in the drawings, it should be understood that the specific structural forms shown in the drawings are merely illustrative of the requirements of the invention and other forms functioning in the same manner may be used. Changes and modifications may be availed of within the spirit and scope of the invention as set forth in the hereunto appended claims.

We claim:

1. In a froth flotation process in which one pulp constituent is floated and other pulp constituents settle and are removed as tailings, the improvement which comprises moving settled solids from the flotation stage into a vortex zone beneath and in direct communication with said flotation stage, continuously discharging a segregated pulp fr-action from the bottom of said vortex zone in a volume less than its intake capacity so as to confine a body of pulp in said zone, and subjecting .the solids so confined to .a vortex action in said vortex zone thereby directing a continuous return flow of lighter or finer solids into said flotation stage and another continuous flow of heavier or coarser solids from the vortex zone with the bottom discharge.

2. In a froth flotation process in which one pulp constituent is floated and other pulp constituents settle and are removed as tailings, the improvement which cornprises moving settled solids from the flotation stage into a vortex zone beneath and in direct communication with said flotation stage, continuously discharging a segregated pulp fraction from the bottom of said vortex zone in a volume less than its intake capacity so as to confine a body of pulp in said zone, subjecting the solids so confined to a vortex action in said vortex zone thereby directing a continuous return flow of lighter or finer solids into said flotation stage and another continuous flow of heavier or coarser solids from the vortex zone with the bottom discharge, and introducing a stream of diluent fluid into said vortex zone to maintain a freeflowing condition in the material being treated.

3. The process of claim 2 in which the fluid stream is introduced in tangential flow adjacent the area of continuous discharge from the vortex zone.

4. A process for concentration of ores or the like in a multi-stage treatment in which a flotation pulp is introduced into a first stage of such a treatment for progressive flow through the succession of stages and one pulp constituent is floated and other pulp constituents settle and are removed as tailings, aerating the pulp in each stage by rotating an impeller adjacent the bottom of each stage with aerating gas delivered thereto for surface removal of a froth concentrate, moving settled solids in at least one flotation stage into a vortex zone maintained beneath its impeller in direct communication with said one stage, continuously discharging a segregated pulp fraction :firom the bottom of said vortex zone in a volume less than its intake capacity so as to confine a body of pulp in said zone, subjecting the solids so confined to a vortex action in said vortex zone thereby directing a continuous return flow of lighter or finer solids into said at least one flotation stage and another flow of heavier or coarser solids into the bottom discharge, continuously removing the heavier or coarser solids from said bottom discharge and subjecting the solids so removed to size reduction, and introducing the reduced solids as feed to a flotation stage.

5. A process for concentration of ores or the like in a multi-stage treatment in which a flotation pulp is introduced into a first stage of such a treatment for progressive flow through the succession of stages and one pulp constituent is floated and other pulp constituents settle and are removed as tailings, aerating the pulp in each stage by rotating an impeller adjacent the bottom of each stage With aerating gas delivered thereto for surface removal of a froth concentrate, moving settled solids in a plurality of said stages into a vortex zo-ne beneath their respective impellers maintained in direct communication with said stages, continuously discharging a segregated pulp fraction from the bottom of the vortex zones in a volume less than their respective intake capacities so as to confine a body of pulp in each said zone, subjecting the solids so confined to a vortex action in said vortex zones thereby directing a continuous return flow of lighter or finer solids into the plurality of flotation stages and another flow of heavier or coarser solids into the respective bottom discharges thereof, continuously removing the heavier or coarser sol-ids from said bottom discharges, subjecting the solids so removed to size reduction, and introducing the reduced solids after size [reduction as feed to a flotation stage.

6. A process for concentration of ores or the like in a multi-stage treatment inWhich a flotation pulp is introduced into a first stage of such a treatment for progressive flow through the succession of stages and one pulp constituent is floated and other pulp constituents settle and are removed as tailings, aerating the pulp in each stage by rotating an impeller adjacent the bottom of each stage with aerating gas :delivered thereto for surface removal of a froth concentrate, moving settled solids in a succession of said stages into a vortex zone beneath their respective impellers maintained in direct communication with said stages, continuously discharging a segregated pulp fraction from the bottom of the vortex zones in a volume less than their respective intake capacities so as to confine a body of pulp in each said zone, subjecting the solids so confined to a vortex action in said vortex zones thereby directing a continuous return flow [of lighter or finer solids into the succession of flotation stages and another flow of heavier or coarser solids into the respective bottom discharges thereof, continuously removing the heavier or coarser solids from said bottom discharges, subjecting the solids so removed to size reduction, and introducing the reduced solids after size reduction as feed to a flotation stage.

7. A process for concentration of ores or the like in a multi-stage treatment in which a flotation pulp is introduced into a first stage of such a treatment for progressive flow through the succession of stages and one pulp constituent is floated and other pulp constituents settle and are removed as tailings, aerating the pulp in each stage by rotating an impeller adjacent the bottom of each stage with aerating gas delivered thereto for surface removal of a froth concentrate, moving settled solids in at least one flotation stage into a vortex zone maintained beneath its impeller in direct communication with said one stage, continuously discharging a segregated pulp fraction from the bottom of said vortex zone in a volume less than its intake capacity so as to confine a body of pulp in said zone, subjecting the solids so confined to a vortex action in said vortex zone thereby directing a continuous return flow of lighter or finer solids into said at least one flotation stage and another flow of heavier or coarser solids into the bottom discharge, introducing the heavier or coarser solids removed from said bottom discharge into a concentration stage for removal of a concentrate product, subjecting the remainder of said fraction to size reduction, and introducing said fraction after size reduction as feed to a flotation stage.

8. A process for reduction of the tailings loss of copper content in concentration of copper bearing ores in hogtrough type flotation apparatus, in which a flotation pulp of copper bearing ore is introduced into the feed end of the hog tnough apparatus and subjected to progressive flow through a succession of agitation stages in said apparatus, aerating the pulp in each stage by rotating an impeller adjacent the bottom of each stage with aerating gas delivered thereto for elevation and removal of a copper hearing froth concentrate, moving settled solids in a plurality of said stages into a vortex zone beneath the respective impellers maintained in direct communication with the stages, continuously discharging a segregated pulp fraction from the bottom of the vortex zones in a volume less than their intake capacities so as to confine a body of pulp in each said zone, subjecting the solids so confined to a vortex action in said vortex zones thereby directing a continuous return flow of lighter or finer solids into the plurality of flotation stages and another flow of heavier or coarser solids including concentrated copper content into the respective bottom discharges thereof, continuously removing the heavier or coarser solids and contained copper from the bottom discharges, subjecting the solids so removed to a classification treatment in which the copper content is separated from the gangue material, and recovering the separated copper values as product.

9. A process for reduction of the tailings loss of copper content in concentration of copper bearing ores in hog-trough type flotation apparatus, in which a a flotation pulp of copper bearing ore is introduced into the feed end of the hog trough apparatus and subjected to progressive flow through a succession of agitation stages in said apparatus, aerating the pulp in each stage by rotating an impeller adjacent the bottom of each stage with aerating gas delivered thereto for elevation and removal of a copper bearing froth concentrate, moving settled solids in a plurality of said stages into a vortex zone beneath the respective impellers maintained in direct communication with the stages, continuously discharging a segregated pulp fraction from the bottom of the vortex zones in a volume less than their intake capacities so as to confine a body of pulp in each said zone, subjecting the solids so confined to a vortex action in said vortex zones thereby directing a continuous return flow of lighter or finer solids into the plurality of flotation stages and another flow of heavier or coarser solids including concentrated copper content into the respective bottom discharges thereof, continuously removing the heavier or coarser solids and contained copper from the bottom discharges, subjecting the solids so removed to a classification treatment in which the copper contentis separated from the gangue material, subjecting the separated copper content to size reduction, and introducing the reduced copper content after size reduction as feed to a flotation stage.

References Cited in the file of this patent UNITED STATES PATENTS 851,600 Latimer Apr. 23, 1907 2,107,289 Denny Feb. 8, 1938 2,122,028 Daman June 28, 1938 2,928,543 Logue Mar. 15, 1960 2,964,179 Loevenstein Dec. 13, 1960 

1. IN A FROTH FLOTATION PROCESS IN WHICH ONE PULP CONSTITUENT IS GLOATED AND OTHER PULP CONSTITUENTS SETTLE AND ARE REMOVED AS TAILINGS, THE IMPROVEMENT WHICH COMPRISING MOVING SETTLED SOLID FROM THE FLOTATION STAGE INTO A VORTEX ZONE BENEATH AND IN DIRECT COMMUNICATION WITH SAID FLOTATION STAGE, CONTINUOUSLY DISCHARGING A SEGREGATED PULP FRACTION FROM THE BOTTOM OF SAID VORTEX ZONE IN A VOLUME LESS THAN ITS INTAKE CAPACITY SO AS TO CONFINE A BODY OF PULP IN SADI ZONE, AND SUBJECTION TTHE SOLIDS TO CONFINED TO A VOTEX ACTION IN SAID VOTEX ZONE THEREBY DIRECTING A CONTINUOUS RETURN FLOW OF LIGHTER OF FINER SOLIDS INTO SAID FLOTTATION STAGE AND ANOTHER CONTINUOUS FLOW OF HEAVIER OF COARSER SOLIDS FROM THE VORTEX ZONE WITH THE BOTTOM DISCHARGE. 